In the past, tubulars have been expanded into casing for the purposes of patching broken casing or to hang a liner string. The casing, in different applications can have different wall thickness for a specific casing size, depending on the particular well requirements. Because of this, there is a problem with using a cone that is driven into a tubular to expand it into a given casing size. If the wedge or cone is a fixed dimension, it can hang up in heavy wall casing, where the need to expand the tubular is less than if the casing had a thinner wall.
In open hole the same problem can arise, as well as other problems. The amount of radial expansion is greater when expanding tubulars, liners, or screens in open hole. The linear footage of expansion is dramatically longer than when securing a liner to casing or patching casing with a tubular. The main purpose of an expanding open hole liner/screen is to get as close to the open hole borehole as possible, to both maximize the internal diameter (for subsequent operations) and to minimize, or eliminate, the annular area between the liner/screen to restrict axial annular flow. An open hole borehole however usually is not consistent in diameter and shape, and may consist of washed out areas as well as sections that may have partially collapsed inward. This makes the use of a fixed-diameter swedge cone somewhat impractical for open hole applications, as it does not have the capacity to adjust with irregularities in the borehole. A fixed-diameter swedge cannot compensate for enlarged holes to provide the borehole wall-to-liner contact, and may prohibit passage through the liner/screen when encountering a collapsed area in the borehole.
In the context of casing patches, a device depicted in U.S. Pat. No. 3,785,193 discloses the use of a mandrel with collets retained in a retracted position for run in. When a shear pin is broken at the desired location, a spring 49 pushes up-hole on the collets. The collets have radially extending pins 35,36, and 37 with end tapers that engage a longitudinally oriented driving pin 40, which is in turn biased by a stack of Bellville washers. In a tight spot during expansion, the collets 31 are pushed radially inwardly as are the radially extending pins. That radial movement is converted to longitudinal movement of the pin 40 against the force of the Bellville washers 43. This design presents several drawbacks. There is no way to retract the collets after the shear pin 51 is broken. This can create potential hang up problems on the removal operation after expansion. This design makes it difficult to adjust the preload on the Bellville washers. Finally, the applied force to keep the collets expanded from the Bellville washers must be transmitted at a right angle while relative movement is contemplated between the pins, such as 35 and the collets 31. This relative movement, in view of the part orientations can result in loads applied to the collets at a point other than directly behind the ridges 31h. If this happens, the collets can be deformed.
Yet other relevant art in the tubular expansion field comprises U.S. Pat. Nos. 3,358,760; 4,487,052; 4,602,495; 5,785,120; 6,012,523; 6,112,818.
Various embodiments of the present invention have been developed to address the shortcomings of the prior designs. In the case of hanging tubulars or liners in casing or patching casing, a flexible swedge has been developed having a movable cone biased by Bellville washers wherein the movable cone is in longitudinal alignment with the collets and ramps them radially when it is advanced longitudinally. This preferred embodiment incorporates a shear release to facilitate retraction of the collets for removal
For open hole applications, a preferred embodiment has been developed to address the unique requirements of large radial expansions, which require high loads in confined spaces and for great distances. The preferred design addresses shortcomings in the fixed-diameter swedge design. The adjustable swedge cone allows and compensates for the irregularities in the open hole borehole. This is accomplished by using a collet-type swedge cone, which allows diametrical variance depending on the state of the dual cone assembly underneath (support structure for the collet). The drive system for the cone assembly is preferably nitrogen gas. A gas drive design is utilized due to the large diametrical range covered by the collet design. Mechanical drive mechanisms, while perhaps simpler, are impractical due to the relatively large axial displacement of the upper drive cone during normal operations of the device (i.e. a Belleville spring stack would be impractically long to allow for such high axial movement at the desired force for liner/screen expansion). A coiled spring would simply be too big in diameter for the available space and the force delivery requirement.
Prior to running in the hole, the multi-stage gas drive assembly is charged (allowing for thermal effects as the tool is run in the hole) to allow approximately 200,000# drive force against the swedge collet. Based on lab testing, this force is sufficient to swedge both solid and perforated (screen) base pipes. In this state the collet is expanded to a designed diameter to allow conformance with the borehole, even in a somewhat enlarged condition. As the swedge is pushed into the un-expanded liner/screen it expands the pipe outwards to the full diameter of the collet. If the hole is undersized or at gauge diameter (diameter drilled) the liner/screen will meet resistance when contacting the wellbore. To push the swedge through, the collet drives the upper cone upward against the nitrogen-charged cylinder assembly. As this occurs, the cone moving upwards allows the swedge collet to retract in diameter until it is allowed to pass through the expanded pipe. The high-pressure chambers of the gas assembly are also compressed, making the pressure increase, and thus the load on the swedge collet. Also, this same process occurs if a collapsed section of the borehole is encountered. The swedge collet simply retracts inward as increased force is applied against the gas-charged drive assembly. The gas-charged drive assembly, for example, will start to move upwards when about a 200,000# load is applied to the collet assembly, and will allow full retraction of the collet when about a 300,000# load is applied.
Another feature of the preferred design is that the gas-charged assembly is independent, and not sensitive to, the bottom hole pressure (hydrostatic). The design of the piston/cylinder assembly allows for force balance regarding hydrostatic pressure. The force generated by the assembly is purely dictated by the pressure differential between the low pressure (LP) and high pressure (HP) gas chambers in the assembly.
Also, a de-activation, or release, feature has been designed into the preferred embodiment of the tool to allow full retraction of the swedge cone in the event the assembly must be pulled form the well in an emergency situation (such as the bottom hole assembly becoming stuck), or once the total liner/screen has been expanded and the bottom hole assembly it to be pulled from the well. The tool in a released condition will not drag in the liner, and possibly get stuck, when pulled from the well. The release mechanism is preferably operated by applying internal pressure sufficient enough to shift the cylinder covering the locking dogs downward, allowing the dogs to become unsupported and free to disengage with the mandrel. This allows the lower stationary cone to move downwards away from the swedge collet, thus de-activating the collet from further expansion. Once de-activated, the tool is locked in this position until pulled out of the hole. These and other features of the invention will be apparent to those skilled in the art from a review of the detailed description of the preferred embodiments, which appears below.